You’ve probably heard that riding muddy trails causes damage and should be avoided, but what damage? How muddy? How do you know if a trail is muddy?
Most land managers in Boulder County close trails open to mountain biking when conditions are such that usage will cause damage. To see official closures (and community crowd-sourced conditions), check out BMA’s Trail Conditions page.
We generally have two main types of soil on the Front Range – clay based and decomposed granite. Trail muddiness depends on a few factors – which type of soil, how well the trail was built to withstand water, and water table level.
Clay Based Soils
Clay based soils do poorly in wet conditions. They soak up that water and hold onto it for a while. Using muddy clay trails can cause deep depressions whether on foot, bike or horse. When the trail dries out, those depressions also stick around and next time it’s wet they collect even more water and perpetuate the cycle. Trail users see this mess and avoid it by going off trail, which either widens the existing trail or creates trail braiding. When this happens, the vegetation is destroyed and it can take several seasons to get it to grow back.
Boulder also has a few areas of higher density clay (the worst at Marshall Mesa) which when wet creates “peanut butter” mud. This mud is so sticky that it can clog your drive train and even break your derailleur.
Decomposed Granite Soil
Decomposed granite soils are exactly what they sound like, tiny bits of granite rock. These areas tend to do very well under wet conditions and there’s nothing to absorb water. Even when these trails are wet, riding through puddles will get you splashed but the trail tread won’t be damaged.
Mixed soils and other factors
Some trail areas have a mixture of soils, or trails that are more one than the other. At Heil Valley Ranch, Picture Rock’s first few miles are clay-based, but Wild Turkey and Ponderosa are more granite or well-armored with rock. Nelson Loop at Hall has sections of both soils. Heil Valley Ranch also has a high water table and natural springs that generally run March-May, depending on snowmelt and rain totals. Clay-based trails that have well maintained drains and/or rock armoring will also do better in wet weather. That’s why it’s important to check official open/closed status before heading out on a ride.
What should you do if you encounter mud or puddles on a trail?
Stay on the trail! Sometimes there’s dry space next to a muddy spot or puddle that allows room to ride next to it and still be on the trail, but if it doesn’t – don’t ride off-trail, ride through the mud or puddle. One or two people going off-trail won’t make much of a difference but when lots of people do, they damage or kill the vegetation and either widen the trail or create a new parallel trail called trail braiding. It’s much easier for trail builders to fix problems with the trail tread than to rehabilitate and reseed the area next to the trail. Keep singletrack single!
So what trails are ok to ride when wet?
In Boulder County, Betasso, Walker Ranch, West Mag and LHOHV are usually the ones that do the best. Lower Bitterbrush at Hall can also be good, as is Maryland Mountain. Farther afield, Buff Creek is great after a rain. In the winter, Devil’s Backbone in Loveland tends to dry out fast after a snow. Check out our Where to Ride page for details.
Want to get instant alerts when trails in Boulder County are officially opened or closed?
City of Boulder (Marshall Mesa, Doudy Draw, Flatirons Vista, Greenbelt Plateau): Text “OSMP” to 888-777 to sign up for updates about trail closures, muddy trails and prescribed burns
Boulder County (Heil Valley Ranch, Hall Ranch, Rabbit Mountain): Sign up for alerts
Erie Singletrack: Sign up for alerts
Check out other Boulder trail conditions resources.